A plastic bottle is typically designed with thin walls to reduce material cost. The disadvantages associated with a thin-walled plastic bottle are that it has a relatively low tolerance for internal and external oxygen permeation, pressure, and heat. The reduced oxygen barrier limits the shelf life of the product inside the bottle, and the low tolerance for pressure and heat limits the selection of processing methods that can be used to fill, cap and otherwise handle the bottle. Conversely, a plastic bottle with a relatively thicker wall provides a greater oxygen barrier and can withstand greater internal and external pressure, as well as external heat. This allows the bottle to exhibit an increased shelf life and be used in more processing methods, including high-temperature filling and vacuum filling.
Further, a bottle made of plastic is typically and substantially flat on the closed body-forming portion surface to allow the bottle to stand upright and move conveniently through processing lines. The disadvantage with a flat-bottom plastic bottle is that for soft drinks and other pressure applications, the best design for the bottom of a bottle is a hemispherical one.
Those in the industry will recognize that the aforementioned disadvantage to a typical bottle, namely thin walls and a flat bottom, are not found in a common bottle preform, the predecessor to a bottle. However, a bottle preform is not made for retail use. There are several features of a bottle perform that make it unsuitable and impractical as a consumer product, such as the downwardly directed axial projection in the form of an elongated gate at the closed end of many bottle performs, the superfluous material predominantly in the closed-end portion and in the lower half of the body-forming portion, the challenge with handling the preform during processing due to the hemispherical bottom, and the inconsistent inner diameter and outer diameter along the body-forming portion.